The present invention relates to exercise treadmills and more particularly to mechanisms for tilting the running or walking platforms of treadmills. Treadmills are typically provided with an endless belt which is driven around a pair of rollers as a platform on which a user runs or walks for exercise. In recent years, a variety of mechanisms have been developed for causing the treadmill to tilt upwardly to simulate the effect of running or walking uphill. Those apparatuses developed to date for tilting treadmills do not stabilize the treadmill against movement in the forward to back or side-to-side directions but rather utilize lifting mechanisms which cause the treadmill to move laterally or forwardly or backwardly and thus render the treadmill less stable.